With an electric hand mixer whip room temperature butter with the two different kinds of sugar for a few minutes.
Mix in the egg and vanilla, just until combined.
Mix flour, salt, and baking soda together then add this mixture to the wet ingredients and fold with the help of a Rubber spatula just until combined. Do not overmix.
Finally, fold in the white chocolate chips and M&M, and make sure to reserve some left to press onto the cookie dough before baking.
Prepare 2 baking pans with parchment paper.
Divide the dough into 10 equal balls (using a Digital scale is handy) and place them onto the parchment papers leaving enough space between them to spread. I recommend baking 5 cookies at once.
Do not soften the surface of the balls, in fact, try to keep it as rough as possible for a nice, crackly surface. Let the cookie dough rest in the fridge for an hour.
Pre-heat oven to 175 C / 347°F (no fan)
After 1h chilling time, press some more M&M and white chocolate chips into the dough then bake the cookies for 15 minutes.
While the cookies are still hot, grab a large diameter cookie cutter and apply circular movements around the cookies, to make them perfectly round.
Let the cookies rest for a few minutes, then carefully remove them from the parchment and let them cool on a Cooling rack.
The cookies will further set as they cool. Store them at room temperature for 2-3 days.
Notes
INGREDIENT NOTES:
Measure your ingredients with a Digital scale for accuracy
Use room temp. ingredients eg. egg and butter
TECHNIQUE NOTES:
Make sure you read my Expert tips section above to maximize your success. A short recipe alone is not able to cover all the necessary details, and science behind baking.
Respect the chilling time in the cookie recipe, do not skip it, or the cookies might end up very flat
Try not to overbake your cookies if you prefer them fudgy and gooey